Supraventricular arrhythmia is a particular type of electrical disturbance of the rhythm of the heart. It is an arrhythmia originating in the upper chambers of the heart, which can lead to an irregular, abnormal heartbeat. Supraventricular arrhythmia is a fairly common occurrence, and as people get older, their chance of experiencing supraventricular arrhythmia will typically increase. Supraventricular arrhythmia itself is not an immediately life-threatening condition. Current research, however, has revealed that supraventricular arrhythmia predisposes a patient to such life threatening conditions as stroke, cardiomyopathy, and congestive heart failure. Consequently, it is important for doctors to be able to detect supraventricular arrhythmia as early as possible, since the earlier that supraventricular arrhythmia is diagnosed and treated, the greater the chance that the arrhythmia or its dangerous side effects can be treated, reducing the risks of stroke, cardiomyopathy, and congestive heart failure. Furthermore, it is important to be able to monitor the arrhythmia over time, since duration is an important factor in evaluating the health risks associated with supraventricular arrhythmia and ongoing monitoring also allows doctors to regulate the amount of medication that patients take as treatment for supraventricular arrhythmia.
Unfortunately, patients often will not even realize that they are experiencing supraventricular arrhythmia, since secondary symptoms may not appear or may be difficult to recognize. The standard technique for detecting arrhythmias employs an electrocardiogram (“ECG”), which uses several electrical leads attached to the patient's chest to monitor the patient's heart during a visit to the doctor's office (where the ECG machine is located). An ECG is a medical diagnostic device that produces a fairly detailed readout of the patient's heart rhythm, which a medical professional may interpret in order to evaluate how a patient's heart is functioning during the visit to the doctor's office. An ECG often does not monitor a patient's real-time beat-to-beat rhythm, however; instead, it may process the patient's heart rhythm over discrete time intervals (such as 5 seconds) to provide a “snapshot” heart rhythm output for interpretation by a medical expert. Consequently, it may be difficult for even medical professionals to detect supraventricular arrhythmia using an ECG. A real-time, beat-by-beat analysis of the patient's heart rhythm would allow for more accurate assessment of a patient's heart rhythm in order to detect the presence of an arrhythmia.
Furthermore, supraventricular arrhythmia is often an intermittent, sporadic condition, such that the use of an ECG during a visit with a doctor may not reveal any irregularity in the heart rhythm, since the patient may not be experiencing the arrhythmia at that time. In such a case, regular (periodic) or continuous monitoring of the patient's heart rhythm would be better able to detect supraventricular arrhythmia. Once supraventricular arrhythmia has been detected, regular monitoring is also recommended in order to determine the duration of the arrhythmia, since sustained supraventricular arrhythmia lasting more than 24 to 48 hours greatly increases the chance of a blood clot forming that could cause a stroke in the patient.
Regular monitoring would also allow for adjustment of the dosage of medications treating the supraventricular arrhythmia (or the secondary symptoms) based upon the patient's daily condition. Once an arrhythmia has been detected, doctors often prescribe blood-thinning drugs (anti-coagulants), such as Coumadin® (Warfarin Sodium), in order to reduce the chances of blood clot formation, or anti-arrhythmia medications, in order to stabilize the heart rate. Unfortunately, both the blood-thinning drugs and the anti-arrhythmia medications may have side effects, some of which can be medically serious. Therefore, doctors may prefer daily monitoring of the patient's heart rhythm for supraventricular arrhythmia, so that they may lower the dosage of drugs that the patient takes as the arrhythmia subsides (as opposed to the current practice of maintaining the same dosage level between doctor visits, which are typically spaced six months apart). This may reduce the side effects experienced by the patient. A device that a patient could use to monitor their heart rhythm, searching for signs of supraventricular arrhythmia, would address all of these needs. Since a patient would operate such a device, it should be simple, portable, convenient, low-cost, self-contained, non-invasive, and automatically assess the patient's likelihood of arrhythmia.
The present invention of the Cardiac Rhythm Monitoring Device (“CRMD”) is designed to perform all of these functions. It is not designed to be used exclusively by doctors as the primary device for sensing, detecting, diagnosing, or classifying arrhythmias. Rather, the CRMD allows for periodic monitoring of the rhythm of a patient's heart, warning the patient if it detects potential supraventricular arrhythmia activity. This can be useful when a doctor suspects that a patient has experienced intermittent supraventricular arrhythmia, but the ECG does not record any abnormal heart rhythms during the visit to the doctor's office. The CRMD can provide a preliminary warning of the possibility of a serious supraventricular arrhythmia, alerting the patient to see a doctor for a more thorough analysis of their rhythms. If the CRMD detects supraventricular arrhythmia for over a 24-hour period, for example, the patient has a greater need for medical attention than if the duration of the arrhythmia is shorter. And, the CRMD can be used in conjunction with blood-thinning medications or anti-arrhythmia medications to regulate the dosage according to the condition of the patient's heart rhythm.
The CRMD may be used in a discrete, periodic manner, or it may be used to continuously monitor the patient's heart rhythm. In the first embodiment, the patient, as described above, would typically use the CRMD periodically. In the second embodiment, however, the CRMD could also be used continuously, which would be especially useful for detecting intermittent supraventricular arrhythmia. In that case, the patient would wear the CRMD continuously throughout the day. This would allow for continuous, uninterrupted monitoring of the patient's heart rhythm, such that the CRMD would be able to warn the patient immediately whenever it detects a potential supraventricular arrhythmia. The patient would then be able to seek prompt medical treatment from medical professionals, who could apply confirmatory tests to verify an arrhythmia and provide the appropriate level of treatment to the patient. For this type of continuous monitoring to be effective, however, the CRMD must not interfere substantially with patient's lifestyle (or else the patient will not wear it). Thus, convenience factors (such as small size, light-weight, and unobtrusive configuration) will be incorporated into the design of the device.